First, we need to address this aspect, particularly and immediately.
If you base your morality on the Bible, then you are obligated to kill gays. It's right there in black and white, no other options. If you pick and choose which part of the Bible to heed (which most sane Christians do) then you are not obligated to kill gays.
You need to stop this. And, trust me, you're not the only one. But it needs to stop right now.
1) Christians who advocate such homicidal arguments are wrong.
2) Do not validate them for the sake of your own personal satisfaction.
3) Do not encourage other Christians to believe such dangerous things by insisting they should.
Seriously: What the hell? Why would you reinforce such beliefs by obliging Christians?
Nor does the point of them being wrong focus on the imposition of modern values unto ancient tradition; this is redletter. That's why it's important for you to lay out the actual argument about enforcing the Law. Don't skip and nudge and wink your way through it; the answer is generally the same, but its specific presentation attends the construction it responds to. You know, like, in what order to say the obvious, since saying it out of order, as if a standardized or doctrinaire catch-all, might accidentally confuse people; it happens a lot with evangelicals.
But, yes, when you acknowledge—
e.g., "Yep."—your dalliance in fallacy, it stands out even more that you would insist they have obligation to homicide. And when we consider the fanaticism your argument obliges of all Christians, indeed, we might hope you should have better reason than self-satisfaction.
Furthermore, my society is experiencing a time when fanatics of diverse fantasies and delusions are actually shooting the place up; it seems unwise to oblige as such a known type that does, in fact, have its place on the current homicidal arc. I'm having a hard time formulating a sentence that encompasses everything you screwed up in that. Seriously, it's not just your formulation obliging all Christians to homicidal righteousness; I'm not utterly unfamiliar with the argument, and one thing worth pointing out is that it does fall under the rubric of letting people you already know are wrong set the terms of discussion. But more importantly, yes, people really are shooting the place up, these days. While the last mass slaughter about homosexuals wasn't a Christian, nor, for instance, the incels necessarily religious, we might recall the magatude, as well as other sociopolitical currents favoring hyperreactionary trends intended to spite critics by fulfilling criticism.
And it's true, that last ought to be some manner of overstatement or exaggerated caution, but even still, the bloodthirsty Christians are wrong, and you're wrong. And while there is a context in which I can appreciate proud bigotry for identifying itself°, that is not what we're dealing with; that is not the sort of outlook you're referring to.
For years, people have been expected to take it easy on certain manners of violent talk, because, well, free speech. But the expectation that people are supposed to chill out and not take everything so seriously is predicated on the idea that the talk isn't literal. You know how it goes, the snowflakes aren't supposed to get so triggered. Trying to ignore it as much as one might didn't work well with the incels; they started shooting in order to get attention. Years of organized political messaging about Latinx invaders officially achieved the White House, and are officially accounted among a terrorist's motives.
So, yeah, watching someone oblige Christians to righteous homicide for the sake of ... uh ... whatever it is you think you're doing, is a little unsettling.
Moving right along:
If you base your morality on the Bible, then you are obligated to kill gays. It's right there in black and white, no other options. If you pick and choose which part of the Bible to heed (which most sane Christians do) then you are not obligated to kill gays.
Show me. And toward that end—
In Matthew 5:18, where Christ tells his followers that the Law (the Old Testament) is to be followed 100%.
—the next question is what the Law said.
Bring it. Please. Truth is, I can put it to rest definitively, so I'm actually curious as to what the actual underlying problem is, that I might figure out how to address it.
(And if we can cover a certain point in advance: If you wish to hand me a source, like someone else's explanation, please do be kind of specific about which parts, because otherwise we can get distracted in side issues about what you didn't mean.)
But how, particularly, do you see what part of the Law being enforced?
Again, that's a part you can decide to disregard, and say that people who heed those words are following the Bible improperly. Or perhaps you think that Jesus was wrong that one time. Or that it was mis-translated. Or he didn't really mean it. Or whatever. No worries. It just means that you are going to end up with a LOT of different interpretations.
Again, it's important for you to lay out the actual argument about enforcing the Law.
†
I wouldn't even know what ostensibly helpful advice to suggest, and this is what that means: Words have meaning, as do the sentences we construct with them. Sometimes, people will talk of contradictions, for instance, in the Bible, and that's not to say they aren't there. But neither are they the same, nor are the points of contradiction necessarily similar in value or function. Your reference to Mt. 5.18 is incomplete, at best; what you would apply it to is your own religious assertion. You think you see something, but can you actually show it to me?
It's important, because I am very much certain I can answer you. I just need to know how you're choosing to address which components of the Law. The answer remains consistent, and what remains is a question of how to make it make sense.
____________________
Notes:
° When they're just fine identifying as bigots and supremacists, that means we can skip past the mincing spectacle of people whining about words like racism and misogyny. Like the magatude, for instance. It's one thing be okay with people chugging milk to puking while pushing white supremacism in hopes of somehow emotionally unsettling other people, but that's the thing, at least with those we have actual data on an element of dangerous stupidity; we know who to avoid. I'm also thinking of a white nationalist organizer in my region who is perfectly proud to boast that he is a racist who wants a white homeland. At least I know he's there. And if I really want to argue with him, at least he's not going to pretend he's not a racist. Thing is, he thinks he's right, and thus not hamstrung by the same neurotic distress we see among so much of the magatude, Christian right, Republican Party, and even mainstream liberals.